1. Field of the Invention
This invention relates to a novel method for masking a substrate prior to painting. More particularly, this invention is concerned with a novel method and composition for forming a mask on a substrate which is to be painted with an air brush, which method and composition are easy to use; can be employed to produce high definition masks for air brush painting; and which can easily be removed after use.
2. Description of the Preferred Embodiments
Air brush painting is widely used in applications from touching up photographs to the creation of original works of art. The basic instrument used in air brush painting is an air brush. An air brush is a type of miniature spray gun which atomizes the liquid desired to be painted into droplets, and allows the spray application of the atomized droplets onto a substrate. An air brush can be used to apply most liquid media. Typically, air brushes are used to apply watercolors, gouaches, acrylic paints, oil paints, and inks. The substrates which can be air brush painted include paper, textiles, glass, metal and plastics. Paper is the most commonly used substrate for air brush painting. Textiles are also an important substrate as air brush painting is used extensively to decorate articles of clothing, such as tee shirts.
Air brush painting to a large extent has replaced the use of conventional artist brushes in commercial an mid other related fields. There are advantages of an air brush in comparison to an artist brush and disadvantages.
A person using artist brushes has to employ a selection of different size and types of brushes. The artist must select the particular size and type of artist brush best suited for the application of the desired paint to an area to be painted. Often a combination of different brushes are used to paint a given area. The bristles of the artist brush are loaded with paint from a palette or the like. The artist brush is then brought into direct contact with the area to be painted and by controlling the movement and pressure on the brush the paint can be made to flow from the bristles onto the substrate. The painting process with an artist brush has to be interrupted at short intervals and the artist brush reloaded with paint to cover even moderate size areas. There is however no need to mask areas of a substrate when using an artist brush as the paint can be selectively applied to a given area and it is possible to paint small features.
An air brush is more versatile and much faster than an artist brush. An air brush can readily be controlled to limit the amount of paint applied to a given area to allow for shading. In addition an air brush can be used to rapidly spray paint on relatively large areas. A person using an air brush does not need a collection of different types and sizes of air brushes like the person using artist brushes. The coverage of a single air brash can be easily controlled by moving the air brash toward or away from the substrate being painted. An air brush also does not have to be repeatedly reloaded with paint. The paint is initially loaded into a reservoir which typically holds enough paint to continuously supply paint to the air brush until the desired area is completely painted. An air brush is much faster to paint with than with artist brushes because of the use of a single instrument, the wider range of control obtainable with an air brush and the elimination of the requirement of frequently reloading with paint. A further advantage of an air brush is that the paint is applied without brush marks.
Air brushes have a significant disadvantage which has limited to their effectiveness and heretofore required the use of artist brushes for detail work in most air brush paintings. As noted above an air brush atomizes the paint and sprays the paint in the form of droplets. The paint which is deposited as a spray does not have the high resolution obtainable with an artist brush but rather the edge of the sprayed area are "fuzzy" due to the spray pattern. In addition, special care must be taken when using an air brush to prevent the paint from being deposited inadvertently or as an over spray on areas not intended to be painted. The inability to obtain a clear demarcation of painted areas with air brush painting is a distinct limitation. This is particularly troublesome when painting features which require fine details such as bird feathers, animal fur, and detailed patterns such as lace. To obtain fine details in air brush painting it has heretofore been necessary to resort to the use of artist brushes, pens and pencils to supplement the air brush.
Masks are used in air brush painting to obtain high definition paintings. The masks are used to obtain sharp edge definition and to protect the masked areas from inadvertent spraying and over spray. The application of a mask however can be very time consuming and tedious work. The masks are shaped to conform to the exact configuration of the area to be masked. It is not unusual for the preparation and application of a mask to take much more time than the actual air brush painting.
The materials used to make the masks include paper, vellum, acetate film and frisket. Paper, vellum and acetate film masks can be cut to the required shape and then mechanically secured to the surface of a substrate with tacks, staples or tape. This method of attachment has the disadvantage that the painted edges of the masked area are softer in definition due to some of the spray going under the edges of the mask. In order to obtain sharp, hard edges it is necessary to secure paper, vellum and acetate film masks tightly to the surface of the substrate with an adhesive such as rubber cement. The application of an adhesive to a mask is a difficult and messy process particularly if the mask has small detailed cutouts. The removal of the adhesive from the substrate after the mask is used is difficult and time consuming.
An additional material used for masking is frisket. Frisket is a ready made masking material available from various commercial sources. Frisket is made of paper or plastic film which has a rubber based adhesive preapplied on one surface which is covered with a removable protective film. In use the frisket is cut to size and then the protective film is removed to secure the frisket mask to a substrate.
All of the mask materials, and methods described, above have proven in use to be unsatisfactory. If the mask is not adhered tightly to the substrate, the painted edges of the masked area are poorly defined. On the other hand if the mask is tightly adhered to the surface of the substrate with an adhesive such as rubber cement, the surface of the substrate can easily be damaged when the mask is removed. Individual fibers can be pulled from the surface of paper and textiles which adversely affect the surface finish. The removal of the rubber adhesive from the surface of the substrate is time consuming, typically involving peeling or robbing the adhesive from substrate.
It has been suggested to use a material, called liquid frisket, to form masks. Liquid frisket is a liquid dispersion of a rubber latex. Liquid frisket is painted on the area to be masked with a brush, and then dried to a continuous film. Liquid frisket has substantial drawbacks which make it particularly unsatisfactory when used on paper and especially unsatisfactory on textile substrates. Liquid frisket, unlike most liquids, cannot be air brushed because liquid frisket clogs air guns. Liquid frisket is too fluid to form details in the coating as applied. After the liquid frisket has dried, the resulting film it is almost impossible to cut details into the mask because of the adhesion of the mask to the substrate. A particular troublesome problem encountered with liquid frisket, is that the mask is very difficult to remove from paper substrates and almost impossible to remove from textile substrates. The liquid frisket as it is applied penetrates and bonds tightly to the individual fibers of paper and textiles. Individual fibers, and even sections of paper are pulled from the surface of paper, when the dried film of liquid frisket is removed from paper by either peeling or rubbing. Even more of a problem, is that the dried film of liquid frisket cannot be removed from textiles by peeling or rubbing as the masking fluid when applied soaks deeply into textiles and become intimately bonded to the individual fibers. The only way to completely remove the dried film from textiles is to use a solvent. This is unsatisfactory because of the adverse effects of the solvent on the applied paint and the textile.
An additional masking technique used in air brush painting is to use an open material such as, screening, lace or cheese cloth, as a stencil. The open material is placed on the surface of the substrate and paint sprayed through the open material onto the underlying substrate. The open material is removed to reveal the openings in the material as the painted area, and the pattern of the material as the unpainted area. This technique has serious disadvantages in that the desired pattern of the open material is formed in a negative pattern, that is, an unpainted area on the substrate. In most situations it is desired to form a positive copy of the open material, such as a lace, directly on the substrate. To obtain a painted pattern of the open material it now necessary to use a base coat of the desired color, and then, apply the background color with the open material in place on the substrate. The requirement of using multiple colors to obtain a positive copy increases the time, and complexity involved in making a painting. A further problem of this method is that the open material cannot easily be tightly adhered to the surface of a substrate. As a result the reproduction of the desired pattern is not sharp as the paint spray tends to pass under the open material.
What would be highly desirable would be a masking method and a masking composition which are easy to use, and can be used to make high definition air brush painting. Preferable the masking composition should be applicable with an air brush; once applied should be able to be shaped to form details in the mask; and would provide an effective high definition masking for air brush painting. It would be especially desirable if the method and composition could be used to make positive masks. Last, but not least, the mask after use should be readily removed without damage to the underlying substrate including paper and in particular textile substrates.